Grinding balls are available in different diameters. The rule of thumb is: for efficient milling the ball should be at least 3 times larger than the largest particle in the sample. To avoid abrasion and wear it is essential to only use balls with identical diameter.
The number of grinding balls depends on the jar volume used. The document “Grinding Jar Ball Charge” in the Downloads section provides details about usable volumes, maximum feed sizes and correct filling of the jars with grinding balls for dry and wet milling as well as cell disruption.
Grinding jars and grinding balls should always be made of the same material.
Available materials:
- Hardened steel (density 7.8 g/cm3; hardness ≤ 235 HB, medium abrasion resistance)
typically used for pulverizing medium-hard to hard and brittle samples.
- Stainless steel (density 7.7 g/cm3; hardness ≤ 245 HB, medium abrasion resistance)
typically used for pulverizing medium-hard to hard and brittle samples.
- Tungsten carbide (density 14.8 g/cm3; hardness 93.6 HRA; high abrasion resistance)
used for grinding very hard, brittle sample materials. By using tungsten carbide, contamination of the sample with iron is prevented.
- Agate (density 2.6 g/cm3; hardness 6.5 – 7 Mohs, low abrasion resistance)
a highly pure natural material suitable for pulverizing soft to medium-hard or fibrous samples. Due to its low-density agate is suitable for gentle grinding processes with low energy input.
- Sintered aluminum oxide (density 3.8 g/cm3; hardness 1600 HV 0.5, medium abrasion resistance) is a ceramic material suitable for grinding soft to medium-hard or fibrous samples. It is mainly used for heavy-metal-free grinding processes.
- Silicon nitride (density 3.6 g/cm3; hardness 1600 HV, high abrasion resistance) is a ceramic material suitable for grinding medium-hard to hard samples. Due to its low density silicon nitride is used for gentle grinding processes with low energy input. Thanks to the high abrasion resistance of the material it is also highly suitable for ultrafine grinding.
- Zirconium oxide (density 6.05 g/cm3; hardness 1250 HV, high abrasion resistance)
ceramic material suitable for pulverizing medium-hard to hard and fibrous samples. It is typically used for heavy-metal-free grinding processes or applications which aim at ultrafine particle sizes.
Please note: The grinding tool material should be harder than the sample. For further information check the “Material Analyses of Equipment & Accessories” document in the Downloads section.
